<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Javascript Study</title>
</head>
<body>
    <script lang="text/Javascript">
        console.log(a);
        var a =3;
        function f(){
            console.log(a);
        }
        f();

        var obj = {};
        f.call(obj);

        console.log('1------------1')
    
    
        function f2(){
            var b= 3;
            f3();
        }
        var b = 5;
        function f3(){
            console.log(b);
        }

        f2();
        console.log('2------------2')
        if(!(c in window)){
            var c = 4;
        }
        console.log(c);
 
    </script>

</body>
</html>